1. Field of the Invention
The present invention relates to a liquid crystal display device and, more particularly, to an art useful in application to a video signal line driving unit (drain driver) of a liquid crystal display device capable of providing multilevel grayscale display.
2. Description of the Related Art
Active matrix liquid crystal display devices which have active elements (for example, thin-film transistors) for individual pixels and drive the active elements in a switching manner are widely used as display devices for notebook personal computers.
In such an active matrix liquid crystal display device, since video signal voltages (grayscale voltages corresponding to individual display data; hereinafter referred to simply as grayscale voltage(s)) to its pixel electrodes via the respective active elements, no crosstalk occurs between the pixels, and unlike a simple matrix liquid crystal display device, multilevel grayscale display can be provided without the need to use a special driving method for preventing crosstalk.
A TFT type of liquid crystal display module is known as one kind of active matrix liquid crystal display device. The TFT type of liquid crystal display module includes a TFT (Thin Film Transistor) type of liquid crystal display panel (TFT-LCD), a drain driver arranged on the top side of the liquid crystal display panel, and a gate driver and an interface block each of which is arranged on any of the sides of the liquid crystal display panel.
The drain driver included in the TFT type of liquid crystal display module is made of one semiconductor chip, and the semiconductor chip has in its inside a multilevel grayscale voltage generation circuit and a multilevel grayscale voltage selection circuit for selecting one grayscale voltage level corresponding to display data, from the multilevel grayscale voltage generated by the multilevel grayscale voltage generation circuit.
This art is disclosed in, for example, Japanese Patent Application Nos. 86668/1996 and 50699/1998.